Effects of water-saturation on strength and ductility of three igneous rocks at effective pressures to 50 MPa and temperatures to partial melting
Instantaneous-failure strengths and ductilities of water-saturated cylindrical specimens of Charcoal Granodiorite, Mount Hood Andesite, and Cuerbio Basalt are determined at a strain rate of 10{sup -4}s{sup -1} and at effective confining pressures (Pe) of 0 and 50 MPa and at temperatures to partial melting. The data indicate: (1) at Pe = 0 and 50 MPa (Pc and Pp of 50 MPa and of 100 and 50 MPa, respectively) the granodiorite does not water-weaken; (2) at these same Pe the more porous and finer-grained andesite begins to exhibit water-weakening at about 600/sup 0/C; (3) at Pe = 0 and 870-900{sup 0}C the andesite's wet strength averages 20 MPa compared to 100 MPa, dry; (4) at Pe = 50 MPa and 920{sup 0}C its wet strength is 45 MPa compared to 160 MPa dry; (5) at Pe = 0, the basalt appears to be water-weakened above 800{sup 0}C; (6) water-saturated specimens deformed at temperatures less than T{sub m} exhibit ultimate strengths at less than 2 percent shortening and then work-soften along faults; and (7) both dry and wet specimens deform primarily by brittle fracture. Extrapolations indicate: (1) crystalline rocks should be drillable because they remain brittle until partial melting occurs, and penetration rates should increase with temperature because there is a corresponding decrease in brittle fracture strength; (2) boreholes in ''water-filled'' holes will be stable to >10 km at temperatures 10 km; and (4) open boreholes in the andesite are apt to be much less stable, and at similar temperatures would fail at 2 to 5-km depth.
- Research Organization:
- Texas A and M Univ., College Station (USA). Center for Tectonophysics
- DOE Contract Number:
- AS05-79ER10361
- OSTI ID:
- 5673638
- Report Number(s):
- DOE/ER/10361-T2; ON: DE83015143
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
152002* -- Geothermal Data & Theory-- Properties of Minerals & Rocks
ANDESITES
BASALT
DUCTILITY
GRANITES
GRANODIORITES
Geothermal Legacy
IGNEOUS ROCKS
MECHANICAL PROPERTIES
MECHANICS
PLUTONIC ROCKS
PRESSURE GRADIENTS
ROCK MECHANICS
ROCKS
SATURATION
STRAINS
TEMPERATURE GRADIENTS
TENSILE PROPERTIES
ULTIMATE STRENGTH
VOLCANIC ROCKS
WATER SATURATION